1. Field of the Invention
This invention relates to the field of actuators, and more particularly to a device which utilizes a shape memory alloy mechanism to change the state of a telephone hookswitch circuit.
2. Description of the Related Art
Telephone headsets are well-known and widely used in business settings. Headsets allow a person to hold a conversation while still having both hands free to operate other devices, take notes, and the like. There are many situations in which a person talking on a telephone would want to be able to move around or away from the telephone in addition to having his or her hands free. For example, a headset user whose telephone base is at his or her desk might be working elsewhere at a table or a filing cabinet while holding a telephone conversation. A cordless headset allows a user to roam further from the telephone base than does a corded headset.
In order to answer or initiate a telephone call with a standard handset telephone, a user simply lifts the handset. This action changes the state of a hookswitch circuit in the telephone base. When the handset is "on hook," the hookswitch circuit is open, and the telephone is not active. When the handset is "off hook," the hookswitch circuit is closed, and the telephone is active and available to make or receive a call. In most handset telephones the state of the hookswitch circuit is changed through the position of a hookswitch in one or more of the wells where the handset rests. In many telephones, the hookswitch is a lever which is pushed out of a slot in the well of a telephone by a spring. When the handset is placed on the telephone base with a portion of the handset in the hookswitch well, the hookswitch is depressed, opening the hookswitch circuit. When the handset is lifted the hookswitch is allowed to spring forward, closing the hookswitch circuit and activating the telephone. In some telephones, the hookswitch is not mechanically activated by a spring, but rather is activated by a magnetic induction circuit in response to the presence or absence of the handset in the telephone base.
Without a special device to control the hookswitch circuit, a headset user must lift the handset off the telephone base in order to put the hookswitch circuit in the "off hook" state before answering or initiating a call. The handset must be kept off the hookswitch for the duration of the call. Headset users may find this annoying since some place other than the telephone base must be found for the handset to rest. Headset users also find the need to remove the handset particularly troublesome since they are required to return to the telephone base to answer or initiate a telephone call. This undermines the utility of a headset, particularly cordless headsets, since the user is not able to answer or initiate calls remotely or in a hands-free manner.
Mechanisms have been devised to displace the handset from the telephone base for headset users. Mechanical lifters have been employed to lift and hold the handset above the hookswitch. Such lifters typically have a lever which is moved or rotated by the user to raise and lower the handset. However, these systems still require users of either corded or cordless headsets to return to the telephone base each time a call is to be answered or initiated. Thus, these devices do not adequately serve the needs of many headset users.
Electro-mechanical lifters use electric motors and gears to effect the lifting of the handset (or other weight placed on the hookswitch). Because this kind of lifter is controlled electrically, it is possible to design an electromechanical lifter system to respond to a remote signal. Such an electromechanical lifter may allow headset users to answer or initiate telephone calls without returning to the telephone base. Electro-mechanical lifters, however, are typically complex and expensive. Their complexity generally results in their being bulky objects which take up desk space next to the telephone base. The expense of electromechanical lifters prohibits their wide acceptance and use, for example in call centers with hundreds or even thousands of users, or by ordinary consumers.
Accordingly, it is desirable to provide an apparatus for operating the hookswitch of a telephone base that overcomes the limitations of conventional products by providing an inexpensive, easy to use apparatus for activating the hookswitch, and that is amenable to remote operation.